146 THE CERATOPSIA. 



The prefrontals form the antero-superior borders of the orbits and give support to the 

 supraorbital horn cores from in front. Anteriorly they overlap the nasals, and laterally they 

 are in contact with the frontals on the inner side and with the lachrymals on the outer side. 



The lachrymals form the anterior borders of the orbits below the prefrontals. They articu- 

 late below with the jugals and in front with the nasals and the ascending branches of the maxil- 

 laries, forming the posterior borders of the lachrymal foramina. 



The jugal is a rather large triradiate bone. Above, it forms the inferior border of the orbit 

 and articulates in front with the lachrymal and maxillary and behind with the postfrontal 

 and squamosal. Together with the last-mentioned element it forms the superior, anterior, 

 posterior, and nearly one-half of the inferior borders of the lateral-temporal foramen. Inferiorly 

 the jugal presents a broad, flat, dependent process, which is closely applied to the quadratojugal, 

 entering into the construction of the quadratojugal arch and aiding in furnishing that support 

 to the quadrate necessary for the suspension and articulation of the powerful lower jaw. On 

 its external surface at its lower extremity the jugal bore a small conical epijugal, triangular in 

 cross section. This latter element is free in the present specimen, but in the skulls of older 

 individuals it is firmly coossified with the jugal. 



The quadratojugal arch, as shown in PI. XLIV, is formed by the jugal, quadratojugal, 

 quadrate, and a small anterior projection from the squamosal. The element most important 

 in its construction is the quadrate, the inferior and anterior end of which is much expanded 

 transversely to form the articulate surface for the lower jaw. From this the quadrate passes 

 upward and backward as a strong shaft of bone expanding posteriorly into a broad, thick blade 

 which articulates with a strong buttress on the lower side of the squamosal and receives into a 

 deep pocket on its inner side the inferior angle of the pterygoid. Externally the quadrate is 

 overlapped posteriorly throughout about one-half of its length by the squamosal, and anteriorly 

 by the quadratojugal, which sends backward a slender process that passes beneath and is 

 overlapped by the anterior projection from the squamosal. The quadratojugal is an irregularly 

 triangular-shaped bone, thick below and thin above, wedged in between the jugal and quadrate 

 in such manner that only its posterior portion is seen when in position. The form and principal 

 characters of the quadrate and quadratojugal are well shown in figs. 17 and 18. 



The nasals. — These are rather massive bones closely applied to one another along the median 

 line, though not coossified. They form the superior and lateral walls of the nasal passage, and are 

 articulated posteriorly with the frontals, prefrontals, and lachrymals. Inferiorly and laterally 

 the nasal articulates with the maxillary and sends forward and downward a long process which 

 meets and overlaps an ascending process from the premaxillary, which latter is wedged in 

 between the maxillary and the nasal. Anteriorly the nasals each send downward a short 

 process. These diverge and receive between them the anterior ascending branches of the premax- 

 illaries. Anteriorly and superiorly the nasals support the single median nasal horn, which is 

 wanting in the present specimen, and which doubtless had its origin in a center of ossification dis- 

 tinct from the nasals, since in a number of instances the nasal horn cores seem to have had only a 

 sutural connection with the nasals. The nasals form the superior border of the external nasal 

 opening, and when seen from the side this border describes a nearly perfect semicircle. The 

 form and characters of the nasals are well shown in fig. 19. 



The maxillaries. — The maxillaries in the present species apparently differ from those of 

 some species of Triceratops in having the lachrymal foramen placed some distance below the 

 naso-maxillary suture. In front the maxillary articulates with the premaxillary and to a limited 

 extent also with the descending process of the nasal. Posteriorly and externally it articulates 

 with the lachrymal and jugal and internally with the palatine and pterygoid. The alveolar 

 border is continuous throughout nearly the entire length of the inferior border of the bone ; on 

 its inner side about 2 inches above the alveolar border there is a series of dental foramina 

 through which passed those blood vessels by which the teeth were nourished during their forma- 

 tion and growth in the dental magazine. The number of these foramina equals that of the 



f See p. 26. 



